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<H1>request_notification(++Name, ++Pred)</H1>
Requests that a predicate be called when an option changes
<DL>
<DT><EM>Name</EM></DT>
<DD>Name of the option
</DD>
<DT><EM>Pred</EM></DT>
<DD>Predicate to call
</DD>
</DL>
<H2>Description</H2>
   Specifies that Pred(Name, OldValue, NewValue) should be called whenever
   the value of the option Name is changed.  OldValue is the old value of
   the option that has just been replaced and NewValue is the new value that
   has just been assigned.  Pred should not modify OldValue or NewValue in
   any way, as this may interfere with other notification predicates.  Note
   also that any choice points left by the call to Pred are pruned upon
   success.

<H3>Modules</H3>
This predicate is sensitive to its module context (tool predicate, see @/2).
<H2>See Also</H2>
<A HREF="../../lib/config_opts/register_option-3.html">register_option / 3</A>, <A HREF="../../lib/config_opts/set_option-2.html">set_option / 2</A>
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